The present invention relates to equipment for tillage of agricultural soil and in particular to a cultivator having a frame adapted to flex at hinge joints while passing over the surface of knolls and depressions found in typical agricultural fields.
Cultivators per se are of course well known. They generally comprise a horizontal frame on which are mounted shanks complete with cultivator shovels such as sweeps or points. The shanks are directed downwardly for tilling soil and the cultivator frame is typically pulled by a farm tractor during cultivating operations.
It is generally desirable to maintain all cultivator shovels at a uniform depth in the soil during cultivating operations. This is particularly so if the cultivator is used as a portion of a seeding apparatus generally known as an "air seeder" to those involved in grain farming. While using an air seeder, if one shovel is shallow in the soil, the seed grain planted behind that shovel may be in drier surface soil and may not germinate as soon as seed grain planted more deeply. Moreover, some of the kernels which are planted shallow may not germinate until after the first rainfall subsequent to seeding. The plants which grow from these late germinating seed grains may lag behind other plants in maturing so that at harvest time the grain harvested may contain some immature kernels. Green and otherwise immature kernels in a grain sample may cause the loss of a grade in quality for the crop with an attendant loss of revenue to the farmer. Likewise, if a shovel is too deep during seeding using an air seeder, the seed grain planted behind that shovel may germinate at the same time as other seed grain but may take longer to emerge from the soil. Plants which emerge later from the soil may reach maturity later depending upon weather conditions.
Cultivator shanks typically are mounted on the frame of a cultivator and adjustment of the depth of working of the shovels in soil is accomplished by adjusting the height of the frame above the soil. However, if the ground is not smooth and the cultivator frame is rigid, some shovels disposed away from the frame support wheels tend to work the soil to either too deep or too shallow a depth.
A cultivator generally has shovels arranged in parallel transversely aligned rows and quite often these rows are three in number. Each row has shovels spaced apart to permit the passage of trash, such as excess straw, between the shovels. The shovels in the rows which follow the leading row are aligned to till that soil not tilled by the shovels in the leading row. It is generally believed that cultivators with only two rows of shovels are more susceptible to being plugged due to collection of trash as they are drawn over fields, as compared to cultivators with three rows of cultivator shovels. This is believed to be because of the closer lateral spacing of cultivator shovels on cultivators with two rows of shovels. Moreover, it is believed that close forward to rearward spacing between rows of cultivator shovels also impedes the free flowing of trash through the cultivator as the cultivator passes over a field. According to this understanding, increasing either the forward to rearward spacing between rows or the number of rows of cultivator shovels tends to improve the ability of a cultivator to pass over trash without collecting it. However, either of the aforementioned increases tends to make control of the depth of cultivation more difficult in conventional cultivators particularly in respect of shovels which are disposed at increased distances from frame support wheels. Thus, there is a need for a cultivator frame which will permit increased control of depth of cultivation while allowing the cultivator shanks to be suitably spaced for permitting trash to clear the cultivator during cultivating operations.